Work controlled centerless grinding machine



June 21, 1955 E. L. DIX 2,711,056

WORK CONTROLLED CENTERLESS GRINDING MAQHINE Filed April 1, 1954 2 Sheets-Sheet l lr J P7206222 MzmiZ/Zz'x June 21, 1955 E. DIX 2,711,056

WORK CONTROLLED CENTERLESS GRINDING MACHINE Filed April 1, 1954 2 Sheets-Sheet 2 United States Patent WORK CONTROLLED CENTERLESS'GRINDING MACHINE Edward L. Dix, Springfield, .Vt., assignor to Bryant Chucking Grinder Company, Springfield, Vt., a corporation of Vermont Application April 1', 1954, Serial No. 420,314

3 Claims. (Cl. 51-103) This invention relates tocenterless grinding machines and particularly of a type where the work piece is rotatably supported on at least two shoes in such a way that the work piece is located by the shoes in proper radial relationship to the work driving means and consequently in correct position to facilitate the entry of the tool in axial direction, and following radial advancement of the work piece and the tool towards each other for the purpose of producing the desired machine operation.

An object of the present invention is to prevent the tool fom entering the working zone in case a work piece has failed to become located in the predetermined correct position.

A further object of the present invention is to stop the machine automatically should thework piece be improperly located.

A still further object is to discontinue the Operation of the machine should the magazine or hopper-that supplies the loading device be empty or if the loading device for some reason should be fouled and the work piece be not placed in the proper working zone.

More specifically this invention requires that a work piece be in proper position for the start of the grinding operation in order that the grinding mechanism be conditioned to perform a grinding cycle.

For a complete understanding of this invention, reference may be had to the accompanying drawings in which Figure l is a front elevation of a centerless grinding machine embodying the invention.

Figure 2 is a wiring diagram for a portion of the machine.

Figure 3 is a detail sectional view to a larger scale on line 3--3 of Figure 1.

Figure 4 is a fragmentary view partly in section on the line 4-4 of Figure 3 of the work spindle, work and work clamp.

Figure 5 is a detail sectional view to a larger scale on line 55 of Figure 3.

This invention is exemplified in a machine of the general type disclosed in Letters Patent granted to Paul A. Grobey, No. 2,671,293 March 9, 1954, for Internal Grinding Machine. It is, however, modified from the Grobey machine to provide difierent means for holding the work piece, the present machine being a centerless grinding machine. As shown it is intended for grinding the internal surface of an annular work piece such as the internal ball raceway 1 shown in Figure 4, grinding this internal'surface concentric with a finished external surface.

As shown the work piece 1 is clamped against an engaging ring 2 carried by the face plate 3 which is secured to the outer end of a rotary spindle 4. This spindle is .journaled in a work head 5, Figure 4 showing one of the bearings 6 by which thisjournaling is effected.

As shown in Figure 4, a plug gage 10 may be employed to determine when the bore of the work piece has been .ground to proper size by the .grinding wheel 11 (see Figure l) rotatably carried by a wheel head 12. In order to make use of a plug gage, the work piece 1 is mounted concentric to the spindle 4, but the .clamp 15. which engages the opposite face of the work piece through the ring element 16 is mounted eccentric thereto and is'rotated by the spindle, in amanner to produce a component offorce in a direction to press the work piece against va ,pair of shoes 20 and 21 (see Figure 5) which support the work piece in concentric relation to the spindle. Mechanism for moving the clamp plate axially to clamp or release the work is not shown herein as it forms no. part ofthe present invention. This general method of supporting the work piece concentric with thespindle and .by an eccentric clamping plate forms subjectv matter. of my application Serial No. 366,217, filed July 6, 1953,..for Centerless Grinding Machines.

Where it is not desired to employ. an automatic gage such as the plug gage 10, the work piece may be mounted in eccentric relation to the spindle as described. .and claimed in Letters Patent No. 2,635,395 granted April .21, 1953 to Arms et al. for Machine-for Grinding .Internal Surfaces Concentric with External Surfaces. event, however, in accordance with this invention, the work piece is to be supported and pressed against-the shoes 20 and 21 inorder to be in proper grinding position.

At- 25 is shown a chute for .holding work pieces .to be ground, and these may drop. downward as they are .used, into operative relation to an ejecting and loading mechanism. This mechanism comprises .a slide 26 which as shown is movable in a direction inclined to the .horizontal and is provided at its upper end witha pivot connection at 28 to a rocker arm 29 carried by arock shaft 30. This rock shaft 30, as shown best inF-igure .1, has. an arm 31 which is connected through a link 32 .to one armof: a bell crank lever 33 fulcrumed at 34 to a stationary portionof the machine. The other arm 35. of this bell crank lever is connected to a horizontally movable 'bar 36 slidable through a guide 3'7 and which is pivoted to the upperend of anactuating lever 38. This lever 38 is journaleclon a fulcrum shaft 3% and its lower end carries .a cam follower roll 49 which is pressed against a cam 41 on a cam shaft 42 as by a spring 43. The slide 26-has .fixed thereto a pointed pin 45 which may pass into the work guide 25 and at times engage beneath the work piece In therein, holding this work piece out of its grinding position. This slide .26 carries an ejector element 46, which when .the slide ispulled upwardly to the left, engages a workpiece resting on the shoes 20 and 21 andpushes it upwardly out of contact with the ,shoe 20 and finally causes it toroll away from the shoe 21 into a suitable .chute 47. This movement of slide 26 also removes the pin 45 from its obstructing position and allows the work piece in to :drop down into grinding position into contact with'the shoes 24) and 21 in the space left empty by the removal of the finished work piece.- This work. ejecting and loading means forms subject matter of my application Serial No. 366,217, filed July 6, 1953, 'hereinbefore referred to.

'The cam shaft 42 has other cams thereon which control other operative portions of the cycle of the machine, as pointed out more fully in the Grobey Letters Patent No. 2,671,293 to which reference has been made, but for the purpose of this invention the work piece handling.

mechanism, and the control for advancing and retracting tht grinding wheel 11 are all that ris-necessary to consider. The grinding wheel 11 is moved aaxially. into and out of grinding position, and for this purpose thewheel head 12 has secured thereto a bracket which is connected through a bar 51 to a lever 52 fulcrumedat 53 and having at an intermediate portion of its length, a cam follower roll 54 which engages a second cam carried by the. cam shaft 42.

This cam shaft also carries a cam 55 which controls a normally open .limit switch LS5. This limit switch LS5 is closed when the main portion of the cam '55 engages In. any

it, but just after the action of the work ejector and feeder occurs, and while the Wheel is retracted in the position of Figure 1, a low point 56 of this cam comes opposite to the switch LS5 and allows it to open momentarily.

In accordance with the present invention, it a work piece has been delivered into grinding position by the Work feeder so that it properly engages with the shoes and 21, the operation of the machine continues, to include the grinding of this newly presented work piece. If, however, the work piece does not reach its grinding position, or should no work piece be then present, the machine will stop when the switch LS5 opens. To this end, each of the shoes 20 and 21 is insulated from the remainder of the machine and forms terminals of a switch, these terminals being bridged by a work piece in proper grinding position which acts therefore as the switch blade.

In Figure 5, the shoe 21 is illustrated being mounted on the insulating spool and being in electrical connection with a wire 61 through a screw 62. This shoe 21 is shown as supporting balls 65 which engage in the raceway groove 66 of the work piece. The shoe 20 which is shown as provided with one ball 67 for engagement with the Work is similarly insulated and has connected thereto the conductor 68. Each of these shoes is mounted for adjustment from and toward the axis of the spindle having a clamp screw such as 70 extending through an enlarged hole 71 in the shoe and threaded into a stationary support 72. An adjusting screw 73 threaded through a block 74 secured to the member 72 by a screw 75 serves to adjust the shoe toward the spindle axis.

In Figure 2 there is illustrated a wiring diagram in accordance with which the desired control of the machine is eifected by the presence or absence of a work piece in grinding position. Such a work piece is shown at 1 in this figure and conductors leading to the supporting shoes 20 and 21 are indicated at 61 and 68. The condoctors 61 and 68 are energized from the secondary of a transformer at low voltage, say, six volts and are in series with the relay coil 99. The primary of transformer 80 is connected to the secondary of a transformer 81 in which 110 volts are generated through the primary of the transformer 81 which is connected across the line voltage leads 82 and 83. The third lead 84, as well as the leads 82 and 83, lead to the main switch 85 of the motor 86 employed to drive the cam shaft 42 as through the reduction gearing at 87. This main switch 85 may be closed by the energization of a solenoid 3m and when so closed, a holding switch 88 is also closed. This switch 88 is in the same circuit with a cam start button 96, which, when closed, completes the circuit from a 110 volt lead 91 through lead 92, closing solenoid 3m, lead 93, starting switch 90, leads 94 and 95, closed switch LS5, and lead 96 to the opposite 110 volt lead 97. Energization of the solenoid 3m, which closes the switch 88, also establishes a holding circuit around the cam start button so that the main switch 85 is held closed so long as the switch LS5 is also closed. This switch LS5, however, is shunted through the lead 100, the relay closed switch CR5, and the lead 98, so that when the switch CR5 is closed as by energization of its closing coil 99, opening of the switch LS5 is ineffective to open the holding circuit for the main switch 85. It will be noted that the coil 99 is in the circuit including the conductors 61 and 68, the work supporting shoes and the work piece 1 when the work piece is in proper position for grinding. Thus whenever a work piece is in position for grinding at the start of a grinding cycle, the opening of the switch LS5 thereafter does not break the motor holding circuit for the cam shaft motor and the cam continues operation, and a grinding cycle is performed. If, however, the relay'CRS is not closed by the presence of a work piece in grinding position, the opening of the switch LS5 immediately opens the holding circuit for the switch 85 which immediately opens and stops the cam motor and with the grinding wheel 11 retracted. To again start the cam motor 86 it is necessary to correct the cause of stoppage and position a work piece in correct position for grinding thereby establishing the proper path for the electric current between leads 61 and 68 and making it possible to again start the machine cycle by momentarily closing the switch 90.

From the foregoing description of an embodiment-of release a work piece therebetween, a pair of angularly.

spaced Work supporting shoes positioned between said face plate and clamp to support the outer peripheral face of such work piece, means actuable to eject a work piece from between said face plate and clamp and to feed another work piece into position therebetween, a grinding wheel, means supporting said wheel for rotation,

means including a rotary shaft for relatively moving said wheel and spindle to perform a grinding cycle between said Wheel and the work piece, means for rotating said shaft, and means responsive to engagement of a work piece on said shoes conditioning said driving means to continue the rotation of said shaft for the start of a grinding cycle.

2 A machine comprising in combination, a rotary work spindle having a face plate at one end, a clamp movable toward and from said face plate to clamp and release a work piece therebetween, a pair of angularly spaced work supporting shoes positioned between said face plate and clamp to support the outer peripheral face of such work piece, means actuable to eject a work piece from between said face plate and clamp and to feed another Work piece into position therebetween, a grinding wheel, means supporting said wheel for rotation, a cam shaft, cams on said shaft, followers for said cams constructed and arranged to produce a cycle of operative motions between said wheel, a work piece.

ejecting and feeding means, and said work pieces, means for rotating said shaft, and means responsive to engagement of a work piece delivered from said feeding means against said shoes conditioning said shaft rotating means to continue rotation of said shaft after ejection of the previous work piece for the start of the next cycle of motions.

3. A machine comprising in combination, a rotary work spindle having a face plate at one end, a clamp movable toward and from said face plate to clamp and release a work piece therebetween, a pair of angularly spaced work supporting shoes positioned between said face plate and clamp to support the outer peripheral face of such Work piece, means actuable to eject a work piece from between said face plate and clamp and to feed another Work piece into position therebetween, a grinding wheel, means supporting said wheel for rotation, a cam shaft, cams on said shaft, followers for said' cams constructed and arranged to produce a cycle of operative motions between said wheel, work piece ejecting and feeding means, and said work pieces,-means for rotating said shaft, means insulating said shoes from said machine, an electrical connection to each shoe closed together by a conductive work piece engaging said shoes when said work piece is in position for operation thereon of said grinding wheel, a motor for driving said shaft, a motor driving circuit including a main switch, a starting switch for said motor, a holding circuit for said main switch shunted around said starting switch, a control switch in said holding circuit, means effective to open said control switch after the end of a grinding cycle, a relay, a circuit having a switch controlled by said relay shunted about said control switch, and a circuit including said 6 2 shoes and closed by the presence of a work piece in References Cited in the file of this patent grinding position and actuating said relay to close said relay controlled switch when a work piece is in position UNITED STATES PATENTS in said machine to be ground and preventing deenergi- 1,745,873 Stoltz Feb. 4, 1930 zation of said holding switch on opening of said control 5 1,979,478 Leland Nov. 6, 1934 switch. 

